From letters to the editor @ the WSJ

SRD

Mr. Lieberman has some worthwhile gripes about washers that take forever to wash poorly, but he struck out in his complaints about gas-furnace regulations. Regulators are trying to encourage the market to adopt more condensing units.

Natural gas is mostly hydrogen, and when it burns, it creates a lot of water vapor (steam), which can be condensed into water. In the past, this latent heat was tossed out, but engineers have developed special heat exchangers that can survive the corrosive atmosphere created when flue gases condense, making practical advanced furnaces that are often 15% more efficient. The savings in fuel costs will more than pay for the cost



My question is, are such appliances available on the market at this time?

Jamie Hall

Yes. Condensing boilers -- called mod/cons -- are actually the most common hot water heating boilers being installed.

The joker in the deck, however, is that they are not suited to some replacement applications, as in order to condense the circulating water temperatures in the baseboards or radiation must be low enough, and many older installations had the radiation designed to operate on higher temperatures.

As to two of your other comments.

First, a 15% increase in efficiency is dreaming. Operating in full condensing mode, it is possible to gain 10% in efficiency over a non-condensing boiler, assuming that both are properly maintained. That is the maximum which is thermodynamically possible. Further, even that gain is only possible, as noted above, when the condensing boiler is, in fact, able to operate in the condensing range, which requires relatively low circulating water temperatures.

Natural gas is NOT mostly hydrogen. In fact, it is almost pure methane, which has the formula CH4. That is, each molecule of methane contains one carbon atom bonded to four hydrogen atoms. When this burns, assuming it burns completely (which it will, in a properly maintained burner) this results in an exhaust gas which is, by volume, one third carbon dioxide and two thirds water vapour.

mattmia2

They've been common for about 30 years. If i recall the model energy code of about 20 years ago is written such that they are required in most instances but in many jurisdictions the energy code is unenforceable.

If you buy quality appliances they clean just fine.

WMno57

SRD said:

My question is, are such appliances available on the market at this time?

Yes. 25 years ago my Father bought a Carrier condensing nat gas furnace. The secondary heat exchanger rotted out. It only lasted 19 years. Which outlasted my father. It did not out last Carrier's 20 year guarantee. It was covered. I got it fixed under warranty, and sold the house. Spoke with the buyer a couple years after the home sale. He was still using the furnace.
Those early plastic clad Carrier secondary heat exchangers did have some failures. Maybe 25 years later they are better.
So buy whatever furnace your trusted local installer likes. If you are worried about service life consider getting an extended warranty.

Hot_water_fan

The savings in fuel costs will more than pay for the cost

My question is, are such appliances available on the market at this time?

These furnaces have long been available. Unlikely they'd save 15% but might pay for their cost in some situations. Condensing boilers, while slightly less efficient than condensing furnaces have bigger savings vs. old boilers without thermal purge. A new, properly installed boiler will probably not give up 15% vs. a mod-con.

mattmia2

WMno57 said:

SRD said:

Those early plastic clad Carrier secondary heat exchangers did have some failures. Maybe 25 years later they are better.

The secondary hx in my lennox is stainless as I think most others also are.